A piston ring assembly is used in assembling together components of the gas turbine engine usually where there is a pressure differential between the sealed components or the pressure differential alternates.
It will be understood that the invention relates to sealing of any housing components with a pressure differential while accommodating relative axial movement and simultaneous radial movement between the two components.
For example, in gas turbine engines that are assembled of numerous coaxial housings and components that require sealing between them, axial and radial motion occurs due to thermal expansion and contraction and due to resilient movement under pressure differential. An example is the conventional sealing between a turbine support case and a vane ring outer shroud. Conventionally, (as shown in FIG. 2 and discussed further below) a sealing ring has a generally triangular cross-section and is used to seal against two orthogonal surfaces sealing both axially and radially. A second inner ring acts as a resilient energizer to apply a resilient biasing force exerted against the triangular sealing ring to maintain the seal. The tension or compression in the energizing ring expands or contracts to wedge between the vane ring and the conical surface of the triangular ring thereby forcing the triangular ring against the axial mating surface and the radial surface in a sealing engagement. The turbine support case generally has a cylindrical sealing surface and the vane ring includes a circumferential groove with axial sealing surface and an axial abutment face against which the energizing ring reacts.
A disadvantage of this conventional arrangement is the requirement to manufacture and assemble two rings in order to accommodate the assembly tolerances, thermal expansion and contraction, as well as displacements caused by any pressure differential. Sealing rings of this type are often replaced during engine overhauls and since the rings are often made from castings to provide better creep properties, the cost of replacing such rings is significant.
It is an object of the invention to provide a low cost piston ring sealing arrangement that can be utilized for newly constructed engines or as a retrofit during regular engine maintenance.
Further objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below.